javaunohelper: WeakBase_Test & MultiTypeInterfaceContainer_Test -> JUnit

Integrate WeakBase_Test and MultiTypeInterfaceContainer_Test in juh tests.
Remove unused import in InterfaceContainer_Test.
Remove getImplementationId() test in WeakBase_Test. Deprecated as of
the commit: 90b27c9493f4225e1612364b5813971b45b681a6

$ make JunitTest_juh

Change-Id: I1205c001e7f15bc5a28289051194fb225e114f13
Reviewed-on: https://gerrit.libreoffice.org/11630
Reviewed-by: David Ostrovsky <david@ostrovsky.org>
Tested-by: David Ostrovsky <david@ostrovsky.org>